Portable communications receivers, and more particularly paging receivers require a substantial battery to power the receiver and decoder electronics in order to provide acceptable battery life. Battery saving circuits are generally employed to reduce the overall power drain of the receiver electronics. Newer technologies, such as microprocessors are being used to integrate a variety of functions, such as those associated with decoding and message presentation to further minimize power consumption. Improvements are still needed to increase battery life, even with the use of new technologies noted above. One such area relates to improvements in battery saving performance which is achievable by modifying system operation based on loading.
Current battery saving methods do not provide for changes of loading on a system. This is especially true in the evening and night hours when the loading on a system is substantially less than the daytime hours. Most battery saving methods provide only predetermined operational characteristics which are constant throughout the day. Adjusting the battery saver operation in lightly loaded periods can greatly increase battery life.
Current battery saving methods are also only effective in conventional paging systems where all receivers are either synchronized to a common transmission or which require long preambles, as in the case of non-synchronous systems. These methods have limited application beyond their originally designed operation. There is a need for a battery saving method which not only improves the performance on a conventional paging system, but which may also be applied to a secondary channel where information received on the primary channel is retransmitted to a second receiver on a secondary channel. Since the transmissions to the primary receiver are completely random, any retransmission of information occurring on the secondary channel would be expected to be completely non-correlated with those of the primary channel. It is contemplated that many retransmissions of information from many different transmitters operating on a common frequency would occur on the secondary channel. In this case, a method of not only providing a battery saving function based on system loading is required, but also one which provides security in the transmission is required to prevent receivers, other than to which the transmission is intended, from receiving the transmitted information.